Bis-EMA addition influence on physical properties of experimental Bis-GMA/TEGDMA-based resin luting agents

Orientadores: Lourenço Correr Sobrinho, Evandro PivaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaResumo: O objetivo deste estudo foi investigar a influência da adição de Bis-EMA sobre propriedades físicas e mecânicas de cimentos resinosos experimentais à base de Bis- GMA/TEGDMA. A partir da mistura de Bis-GMA e TEGDMA na proporção de 50:50 em peso (R01), o monômero Bis-EMA foi gradualmente incorporado à mistura, 10% em peso por vez, definindo onze formulações adicionais com as seguintes proporções entre Bis- GMA/TEGDMA/Bis-EMA: 50/40/10 (R02), 50/30/20 (R03), 50/20/30 (R04), 50/10/40 (R05), 50/0/50 (R06), 40/10/50 (R07), 30/10/60 (R08), 20/10/70 (R09), 10/10/80 (R10), 0/10/90 (R11) e 0/0/100 (R12). Canforoquinona (0,4%), N,N-dimetil-p-toluidina (0,8%) e hidroquinona (0,2%) foram dissolvidas em cada mistura, às quais foram adicionados 60% em peso de partículas de vidro silanizadas. O grau de conversão foi avaliado por espectroscopia infravermelha em tempo real. A resistência flexural e módulo de elasticidade foram analisados em teste de flexão de três pontos. A espessura de película foi mensurada colocando os materiais entre placas de vidro polidas. A dureza Knoop foi determinada em um microdurômetro, com carga de 50g por 15s. A sorção de água e a solubilidade foram avaliadas por meio de alteração de peso das amostras após imersão em água destilada por sete dias. Os dados foram separadamente submetidos à Análise de Variância e teste de Tukey (a = 0,05). As médias para grau de conversão (%) variaram entre 49,8 (R10) e 65,0 (R06). A substituição de TEGDMA por Bis-EMA aumentou a conversão de ligações duplas, enquanto a substituição de Bis-GMA por Bis-EMA não apresentou influência significativa. No teste de flexão, as médias (MPa) variaram entre 104 (R10) e 131 (R02), mas nenhuma diferença significativa entre os grupos foi detectada. Para o módulo de elasticidade, enquanto a substituição de TEGDMA por Bis-EMA não apresentou influência significativa, a substituição de Bis-GMA por Bis-EMA diminuiu significativamente os valores, com médias (GPa) variando entre 5,41 (R09) e 9,59 (R04). As médias de espessura de película (µm) variaram entre 29,3 (R01) e 66,7 (R06), com a substituição de TEGDMA por Bis-EMA gradualmente aumentando os valores, e R04-06 apresentando películas significativamente mais espessas. Médias para dureza (kg/mm2) variaram entre 35,5 (R01) e 47,9 (R05), com a substituição de TEGDMA por Bis-EMA aumentando gradualmente a dureza, exceto para R06, enquanto a substituição de Bis-GMA por Bis-EMA não apresentou efeito significativo. Uma gradual diminuição na sorção de água foi verificada à medida que TEGDMA e Bis- GMA foram sendo substituídos por Bis-EMA, com médias (µg/mm3) variando entre 48,96 (R01) e 15,68 (R12). Médias para solubilidade variaram entre 4,55 (R04) e 9,77 (R02), sem diferença significativa observada entre os grupos. Em geral, os achados do presente estudo mostram que, dependendo da quantidade de Bis-EMA substituindo Bis-GMA e/ou TEGDMA, maior conversão de monômeros ou menor módulo de elasticidade foram detectados. Por outro lado, a substituição de TEGDMA por Bis-EMA aumentou a dureza e diminuiu a sorção de água, embora um aumento na espessura de película tenha sido detectado para algumas misturas. Além disso, a substituição de Bis-GMA por Bis-EMA apresentou influência significativa na diminuição da sorção de águaAbstract: The aim of this study was to investigate the influence of Bis-EMA addition on physical and mechanical properties of experimental resin luting agents based on Bis- GMA/TEGDMA. Starting from a 50:50 wt:wt ratio blend of Bis-GMA and TEGDMA (R01), the Bis-EMA monomer was gradually added to the mixture, 10wt% at a time, defining eleven additional formulations with the following Bis-GMA/TEGDMA/Bis-EMA ratios: 50/40/10 (R02), 50/30/20 (R03), 50/20/30 (R04), 50/10/40 (R05), 50/0/50 (R06), 40/10/50 (R07), 30/10/60 (R08), 20/10/70 (R09), 10/10/80 (R10), 0/10/90 (R11) and 0/0/100 (R12). Camphorquinone (0.4%), N,N-dimethyl-p-toluidine (0.8%) and hydroquinone (0.2%) were dissolved in each mixture, which were loaded to a constant 60wt% with silanated glass fillers. Degree of conversion was assessed by real-time infrared spectroscopy. Flexural strength and elastic modulus were determined in a three-point bending test. Film thickness was measured by placing the materials between optically flat glass plates. Knoop hardness evaluation was carried out through an indenter, with a load of 50g for 15s. Water sorption and solubility were assessed by weight alteration of samples after storage in distilled water for seven days. Data were separately submitted to Analysis of Variance and Tukey's test (a = 0.05). Means for degree of conversion (%) varied between 49.8 (R10) and 65.0 (R06). Replacing TEGDMA with Bis-EMA caused an increase in conversion of double bonds, while the substitution of Bis-GMA by Bis-EMA had no significant influence. Means for flexural strength (MPa) varied between 104 (R10) and 131 (R02), but no significant difference among groups was detected. For the elastic modulus, while replacing TEGDMA with Bis-EMA had no significant influence, the replacement of Bis-GMA by Bis-EMA significantly decreased the values, with means (GPa) varying between 5.41 (R09) and 9.59 (R04). Film thickness means (µm) varied between 29.3 (R01) and 66.7 (R06), with the substitution of TEGDMA by Bis-EMA gradually increasing the film values, and R04-06 showing significantly thicker films. Hardness means (KHN, kg/mm2) varied between 35.5 (R01) and 47.9 (R05), with the replacement of TEGDMA by Bis-EMA gradually increasing hardness, except for R06, while replacing Bis-GMA with Bis-EMA had no significant effect. A gradual decrease in water sorption was detected as TEGDMA and Bis-GMA were gradually replaced by Bis-EMA, with means (µg/mm3) varying between 48.96 (R01) and 15.68 (R12). Solubility means (µg/mm3) varied between 4.55 (R04) and 9.77 (R02), with no significant differences detected among groups. In general, the present findings show that, depending on the amount of Bis-EMA replacing Bis-GMA and/or TEGDMA, increased monomer conversion or decreased elastic modulus were detected. On the other hand, replacing TEGDMA with Bis-EMA increased hardness and decreased water sorption, although an increase in film thickness has been detected for some mixtures. Also, the substitution of Bis-GMA by Bis-EMA had a significant influence on decreasing water sorptionMestradoMateriais DentariosMestre em Materiais Dentário

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